Due to rapid innovation in the electronic communication technology, dual-band or triple-band mobile cellular phones are available in the market, lately. For a businessman who travels a lot, a mobile phone with dual-band capability is preferred since the mobile phone can switch frequencies once required. In other words, it can operate in dual bands (such as 800-MHz and 1900-MHz). Most users prefer a compact mobile phone to a bulky-size one since the former has high reliability in the signal transmitting and receiving ability. In order to achieve high reliability in the transmitting and receiving signals, the quality and functionality of the antenna assembly play a major role in the mobile phone. It is therefore the prime object of the manufacture to improve the functionality of the quality of the antenna assembly in the cellular-phone handset.
FIG. 1 shows a conventional built-in single frequency band antenna assembly used in a mobile phone, is inverted F-shaped, and includes a radiating metal plate 10, a ground metal layer 12, a feeding leg 14 and an open-end connecting leg 16, wherein an etching operation is carried out to extend the feeding leg 14 through an opening 18 in the ground metal layer 12 in order to couple with the radiating metal plate 10. The feeding leg 14 and the ground metal layer 12 are not connected to each other in order to avoid a short circuit problem.
The aforesaid conventional antenna assembly is generally fabricated in the mobile phone such that the latter possesses a fashion design as far as the external appearance is concerned when compared to those mobile phones having externally-mounted antenna assemblies. The built-in antenna assembly requires lesser assembling steps, thereby shortening the production time of the mobile phone. However, the built-in antenna assembly is said to suffer from insufficient of communication band and impedance matching phenomenon, which, in turn, results in difficulties during the designing process of the built-in antenna assembly.